1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same.
2. Description of the Related Art
The conventional semiconductor device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-298005 (P2003-298005A) includes solder balls as connecting terminals for external connection outside the size of a silicon substrate. Therefore, this semiconductor device has a structure in which a silicon substrate having a plurality of connecting pads on its upper surface is adhered to the upper surface of a base plate via an adhesive layer, an insulating layer is formed on the upper surface of the base plate around the silicon substrate, an upper insulating film is formed on the upper surfaces of the silicon substrate and insulating layer, upper interconnections are formed on the upper surface of the upper insulating film and connected to the connecting pads of the silicon substrate, portions except for connecting pad portions of the upper interconnections are covered with an uppermost insulating film, and solder balls are formed on the connecting pad portions of the upper interconnections.
In this conventional semiconductor device, the silicon substrate is adhered to the upper surface of the base plate via the adhesive layer provided therebetween. This increases the total thickness by the thickness of the adhesive layer. Also, during reflow (the temperature is 240° C. to 260° C.) when the semiconductor device is mounted on a circuit board via the solder balls, voids and water in the adhesive layer expand. This adversely affects the adhesive force, and deteriorates the reliability of adhesion of the silicon substrate to the base plate.